Ni-mn-al-co-ferrite



United States Patent "ice 3,245,911 Ni-Mn-Al-Co-FERRITE Avnir Vassiliev, Jean Nicolas, and Mieczyslaw Hildebrandt, all of Paris, France, assignors to Compagnie I( ivenerale de Telegraphic sans Fil, a corporation of rance No Drawing. Filed Dec. 4, 1961, Ser. No. 156,927 Claims priority, appligaton France, Dec. 13, 1960,

3 Claims. (21. 252-625) The present invention relates to ferrites used in electromagnetic microwave transmission systems. More particularly it relates to ferrite used in so-called resonanceisolator devices and which are in the shape of fiat pieces positioned against the large wall of rectangular waveguides building up such devices.

It is known that, when the saturation moment of the ferrite is high, the field necessary for a resonance isolator is also high. At high powers, in microwave ranges, ferrites having a high saturation moment are generally used, such as Ni-, Coand Mn-ferrites.

The production of such a high field requires the use of very bulky, heavy, and highly uneconomical magnets. In certain applications, it would be desirable to reduce the saturation moment of these ferrites without, however, affecting in any significant degree their other characteristics.

According to the invention, this effect is obtained by providing a ferrite material corresponding to the following formula:

xNiO, yCoO, zMnO vFe O wA1 O where:

x=4950 moles y=l.2-1.6 moles z=0.8-1.2 moles v=46-41 moles w=3-7 moles The two preferred compositions correspond, respectively, to

x=49.4 moles x=49.4 moles y=1.4 moles y=l.4 moles z=l mole z=1 mole v=45.1 moles v=42 moles w=3.1 moles w=6.2 moles (b) G. Fegog CoO 33.68 MnO 0.96 270 g. of mixture (a) 30 g. of mixture (b) 2.06 g. of MnO (d) G. A10 28.25 NiO 21.75

All these mixtures are finely crushed with distilled water and calcined at a temperature of 950 C., during This composition is finely crushed with distilled water, dried and transformed into granules by adding a known binding agent containing polyvinyl alcohol.

The samples are compressed at 1T/ cm. and the pieces are sintered at a temperature of 1300 C. during two hours; cooling is then effected at the rate of C./hour.

Example 2 The same method as in Example 1 is used, the composition being formulated as follows (2):

G. Mixture (a) 202.5 Mixture (c) 67.5 Mixture (d) 30 Mn0 1.55

The characteristics of the products obtained in the two examples are listed in the follownig table, where they are compared with those of a conventional ferrite composition:

Conventional Formula (1) Formula (2) ierrite Example (1) Example (2) Maximum induction Bm at 25 oersted, (in

gauss) 1. 900 1. 500 900 Remanent induction Br (gauss) 1. 100 700 400 Coercive field Hc (oerste 8 8 8 Specific gravity (g [cm 5 5 4. 7 Resistivity (megohm/cm.) 1 100 500 Dielectric constant (at 1 mc./ 14 14 Tangent of the loss angle (tg) at (1 mc.ls.) 100. 10- 100.10- Dielectric constant (at 10 mc./s.) 11 11 Tangent oi the loss angle (at 10 mc./s.) 100. 10- 30. 10 20.10 Saturation moment, 4 .Ts/cm. at 20 C. (in

E.M.U., O.G.S.) 3. 200 2. 600 2, 000

The invention will be described in connection with the following examples:

NiO (pure) It is seen that the saturation moment decreases considerably when the Al-contents increases.

On the other hand, the width of the resonance line, measured at 9000 mc./s., is:

500 oersted for the conventional ferrite 500 oersted for the composition (1) 500 oersted for the composition (2) 33 i.e., the same for all three compositions.

Patented Apr. 12, 1966 described hereinabove are not limitative.

It is to be undist'od accurately the proportions cif the constituents, the resulting product being morerhomogeneous.

What is claimed is: 1. Aferrite composition having thetfollowing formula xNiO, yCoO, zMnO vFe 0 wA1 O where: x=4950 moles y=1.2-1.6 moles z=0.81.2 moles 1 :46-41 moles i y fl. V V

2. A' ferrite composition according to claim 1 in which x=49i4 moles F Y y=l.4 i dies i=1 mole w ll moles v=45.1 moles 3. A ferrite composition according to claim 1 in which x=49.4 moles y=1.4 moles I 1 mole r. v=4 2 (moles V w :6.22n'io1cs' v Reteren ces Cited by the liixa miner UNiTEtj TATES PATENTS 11/l9 55 Harvey 1 252-625 5/19'61 Baird et a1; i.: 252-62.5 1/1962 Sin /etz 252--62.5

TOBIAS E. LEVOW,'Prii1 iaiy Exam-mat;

JOSEPH R; LllERlVlAN, MAUlilClS A. fi'RiNDi si,

- Examiners, 

1. A FERRITE COMPOSITION HAVING THE FOLLOWING FORMULA XNIO, YCOO, ZMNO2, VFE2O3, WAL2O3, WHERE: X=49-50 MOLES Y=1.2-1.6 MOLES Z=0.8-1.2 MOLES V=46-41 MOLES W=3-7 MOLES 